| 1. |
- Herrero-Illana, R., et al.
(författare)
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Molecular gas and dust properties of galaxies from the Great Observatories All-sky LIRG Survey
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 628
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Tidskriftsartikel (refereegranskat)abstract
- We present IRAM-30 m Telescope (CO)-C-12 and (CO)-C-13 observations of a sample of 55 luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) in the local universe. This sample is a subset of the Great Observatory All-Sky LIRG Survey (GOALS), for which we use ancillary multi-wavelength data to better understand their interstellar medium and star formation properties. Fifty-three (96%) of the galaxies are detected in (CO)-C-12, and 29 (52%) are also detected in (CO)-C-13 above a 3 sigma level. The median full width at zero intensity (FWZI) velocity of the CO line emission is 661 km s(-1), and similar to 54% of the galaxies show a multi-peak CO profile. Herschel photometric data is used to construct the far-IR spectral energy distribution of each galaxy, which are fit with a modified blackbody model that allows us to derive dust temperatures and masses, and infrared luminosities. We make the assumption that the gas-to-dust mass ratio of (U)LIRGs is comparable to local spiral galaxies with a similar stellar mass (i.e., gas/dust of mergers is comparable to their progenitors) to derive a CO-to-H-2 conversion factor of = 1.8(-0.8)(+1.3) M-circle dot (K km s(-1) pc(2))(-1); such a value is comparable to that derived for (U)LIRGs based on dynamical mass arguments. We derive gas depletion times of 400 600 Myr for the (U)LIRGs, compared to the 1.3 Gyr for local spiral galaxies. Finally, we re-examine the relationship between the (CO)-C-12/(CO)-C-13 ratio and dust temperature, confirming a transition to elevated ratios in warmer systems.
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| 2. |
- Privon, G., et al.
(författare)
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EXCITATION MECHANISMS FOR HCN(1-0) AND HCO+ (1-0) IN GALAXIES FROM THE GREAT OBSERVATORIES ALL-SKY LIRG SURVEY
- 2015
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 814:1
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Tidskriftsartikel (refereegranskat)abstract
- We present new Institut de Radioastronomie Millimetrique (TRAM) 30 m spectroscopic observations of the similar to 88 GHz band, including emission from the CCH (N = 1 -> 0) multiplet, HCN (J = 1 -> 0), HCO (J = 1 -> 0), and HNC (J = 1 -> 0), for a sample of 58 local luminous and ultraluminous infrared galaxies from the Great Observatories All-sky LIRG Survey (GOALS). By combining our new TRAM data with literature data and Spitzer /IRS spectroscopy, we study the correspondence between these putative tracers of dense gas and the relative contribution of active galactic nuclei (AGNs) and star formation to the mid-infrared luminosity of each system. We find the HCN (1-0) emission to be enhanced in AGN-dominated systems (L'(HCN(1 0))/ L'(HCO+(1-o))) = 1.84), compared to composite and starburst-dominated systems (L'HCN(1413/(1-0)) = 1.14, and 0.88, respectively). However, some composite and starburst systems have LH/ CN (1 0) /LH/ CO (1 0) ratios comparable to those of AGNs, indicating that enhanced HCN emission is not uniquely associated with energetically dominant AGNs. After removing AGN-dominated systems from the sample, we find a linear relationship (within the uncertainties) between logio(L'(HCN(1-0))) and log(10)(LIR), consistent with most previous findings. Lc N(1 0) /LIR, typically interpreted as the dense-gas depletion time, appears to have no systematic trend with LIR for our sample of luminous and ultraluminous infrared galaxies, and has significant scatter. The galaxyintegrated L'(HCN(1-0)) and L'(HCO+(1-0)) emission do not appear to have a simple interpretation in terms of the AGN dominance or the star formation rate, and are likely determined by multiple processes, including density and radiative effects.
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| 3. |
- Xu, C. K., et al.
(författare)
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ALMA observationsof warm dense gas in NGC 1614-breaking of the star formation law in the central kiloparsec
- 2015
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 799:1
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Tidskriftsartikel (refereegranskat)abstract
- We present ALMA Cycle-0 observations of the CO (6-5) line emission and of the 435 mu m dust continuum emission in the central kiloparsec of NGC 1614, a local luminous infrared galaxy at a distance of 67.8 Mpc (1 '' = 329 pc). The CO emission is well resolved by the ALMA beam (0.'' 26x0.'' 20) into a circumnuclear ring, with an integrated flux of f(C O(6-5)) = 898 (+/- 153) Jy km s(-1), which is 63(+/- 12)% of the total CO (6-5) flux measured by Herschel. The molecular ring, located between 100 pc
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| 4. |
- Armus, Lee, et al.
(författare)
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GOALS-JWST: Mid-infrared Spectroscopy of the Nucleus of NGC 7469
- 2023
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 942:2
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Tidskriftsartikel (refereegranskat)abstract
- We present mid-infrared spectroscopic observations of the nucleus of the nearby Seyfert galaxy NGC 7469 taken with the MIRI instrument on the James Webb Space Telescope (JWST) as part of Directors Discretionary Time Early Release Science program 1328. The high-resolution nuclear spectrum contains 19 emission lines covering a wide range of ionization. The high-ionization lines show broad, blueshifted emission reaching velocities up to 1700 km s−1 and FWHM ranging from ∼500 to 1100 km s−1. The width of the broad emission and the broad-to-narrow line flux ratios correlate with ionization potential. The results suggest a decelerating, stratified, AGN-driven outflow emerging from the nucleus. The estimated mass outflow rate is 1-2 orders of magnitude larger than the current black hole accretion rate needed to power the AGN. Eight pure rotational H2 emission lines are detected with intrinsic widths ranging from FWHM ∼125 to 330 km s−1. We estimate a total mass of warm H2 gas of ∼1.2 × 107 M ⊙ in the central 100 pc. The PAH features are extremely weak in the nuclear spectrum, but a 6.2 μm PAH feature with an equivalent width of ∼0.07 μm and a flux of 2.7 × 10−17 W m−2 is detected. The spectrum is steeply rising in the mid-infrared, with a silicate strength of ∼0.02, significantly smaller than seen in most PG QSOs but comparable to other Seyfert 1s. These early MIRI mid-infrared IFU data highlight the power of JWST to probe the multiphase interstellar media surrounding actively accreting supermassive black holes.
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| 5. |
- Bianchin, Marina, et al.
(författare)
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GOALS-JWST: Gas Dynamics and Excitation in NGC 7469 Revealed by NIRSpec
- 2024
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 965:2
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Tidskriftsartikel (refereegranskat)abstract
- We present new JWST NIRSpec integral field spectroscopy (IFS) data for the luminous infrared galaxy NGC 7469, a nearby (70.6 Mpc) active galaxy with a Seyfert 1.5 nucleus that drives a highly ionized gas outflow and a prominent nuclear star-forming ring. Using the superb sensitivity and high spatial resolution of the JWST instrument NIRSpec IFS, we investigate the role of the Seyfert nucleus in the excitation and dynamics of the circumnuclear gas. Our analysis focuses on the [Fe ii], H2, and hydrogen recombination lines that trace the radiation/shocked-excited molecular and ionized interstellar medium around the active galactic nucleus (AGN). We investigate gas excitation through H2/Brγ and [Fe ii]/Paβ emission line ratios and find that photoionization by the AGN dominates within the central 300 pc of the galaxy except in a small region that shows signatures of shock-heated gas; these shock-heated regions are likely associated with a compact radio jet. In addition, the velocity field and velocity dispersion maps reveal complex gas kinematics. Rotation is the dominant feature, but we also identify noncircular motions consistent with gas inflows as traced by the velocity residuals and the spiral pattern in the Paα velocity dispersion map. The inflow is 2 orders of magnitude higher than the AGN accretion rate. The compact nuclear radio jet has enough power to drive the highly ionized outflow. This scenario suggests that the inflow and outflow are in a self-regulating feeding-feedback process, with a contribution from the radio jet helping to drive the outflow.
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| 6. |
- Bohn, Thomas, et al.
(författare)
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GOALS-JWST: NIRCam and MIRI Imaging of the Circumnuclear Starburst Ring in NGC 7469
- 2023
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 942:2
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Tidskriftsartikel (refereegranskat)abstract
- We present James Webb Space Telescope (JWST) imaging of NGC 7469 with the Near-Infrared Camera and the Mid-InfraRed Instrument. NGC 7469 is a nearby, z = 0.01627, luminous infrared galaxy that hosts both a Seyfert Type-1.5 nucleus and a circumnuclear starburst ring with a radius of ∼0.5 kpc. The new near-infrared (NIR) JWST imaging reveals 66 star-forming regions, 37 of which were not detected by Hubble Space Telescope (HST) observations. Twenty-eight of the 37 sources have very red NIR colors that indicate obscurations up to A v ∼ 7 and a contribution of at least 25% from hot dust emission to the 4.4 μm band. Their NIR colors are also consistent with young (<5 Myr) stellar populations and more than half of them are coincident with the mid-infrared (MIR) emission peaks. These younger, dusty star-forming regions account for ∼6% and ∼17% of the total 1.5 and 4.4 μm luminosity of the starburst ring, respectively. Thanks to JWST, we find a significant number of young dusty sources that were previously unseen due to dust extinction. The newly identified 28 young sources are a significant increase compared to the number of HST-detected young sources (4-5). This makes the total percentage of the young population rise from ∼15% to 48%. These results illustrate the effectiveness of JWST in identifying and characterizing previously hidden star formation in the densest star-forming environments around active galactic nuclei (AGN).
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| 7. |
- Buiten, Victorine A., et al.
(författare)
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GOALS-JWST: Mid-infrared Molecular Gas Excitation Probes the Local Conditions of Nuclear Star Clusters and the Active Galactic Nucleus in the LIRG VV 114
- 2024
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 966:2
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Tidskriftsartikel (refereegranskat)abstract
- The enormous increase in mid-IR sensitivity and spatial and spectral resolution provided by the JWST spectrographs enables, for the first time, detailed extragalactic studies of molecular vibrational bands. This opens an entirely new window for the study of the molecular interstellar medium in luminous infrared galaxies (LIRGs). We present a detailed analysis of rovibrational bands of gas-phase CO, H2O, C2H2, and HCN toward the heavily obscured eastern nucleus of the LIRG VV 114, as observed by NIRSpec and the medium resolution spectrograph on the Mid-InfraRed Instrument (MIRI MRS). Spectra extracted from apertures of 130 pc in radius show a clear dichotomy between the obscured active galactic nucleus (AGN) and two intense starburst regions. We detect the 2.3 μm CO bandheads, characteristic of cool stellar atmospheres, in the star-forming regions, but not toward the AGN. Surprisingly, at 4.7 μm, we find highly excited CO (T ex ≈ 700-800 K out to at least rotational level J = 27) toward the star-forming regions, but only cooler gas (T ex ≈ 200 K) toward the AGN. We conclude that only mid-infrared pumping through the rovibrational lines can account for the equilibrium conditions found for CO and H2O in the deeply embedded starbursts. Here, the CO bands probe regions with an intense local radiation field inside dusty young massive star clusters or near the most massive young stars. The lack of high-excitation molecular gas toward the AGN is attributed to geometric dilution of the intense radiation from the bright point source. An overview of the relevant excitation and radiative transfer physics is provided in an appendix.
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| 8. |
- Drake, A. B., et al.
(författare)
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The MUSE Hubble Ultra Deep Field Survey VI. The faint-end of the Lyα luminosity function at 2.91
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 608
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Tidskriftsartikel (refereegranskat)abstract
- We present the deepest study to date of the Ly alpha luminosity function in a blank field using blind integral field spectroscopy from MUSE. We constructed a sample of 604 Ly alpha emitters (LAEs) across the redshift range 2.91 < z < 6.64 using automatic detection software in the Hubble Ultra Deep Lield. The deep data cubes allowed us to calculate accurate total Ly alpha fluxes capturing low surface-brightness extended Ly alpha emission now known to be a generic property of high-redshift star-forming galaxies. We simulated realistic extended LAEs to fully characterise the selection function of our samples, and performed flux-recovery experiments to test and correct for bias in our determination of total Ly alpha fluxes. We find that an accurate completeness correction accounting for extended emission reveals a very steep faint-end slope of the luminosity function, alpha, down to luminosities of log(10) L erg s(-1) < 41.5, applying both the 1/V-max and maximum likelihood estimators. Splitting the sample into three broad redshift bins, we see the faint-end slope increasing from -2.03(-0.07)(+1.42) at z approximate to 3.44 to -2.86(-infinity)(+0.76) Z approximate to 76 at z approximate to 5.48, however no strong evolution is seen between the 68% confidence regions in L*-alpha parameter space. Using the Ly alpha line flux as a proxy for star formation activity, and integrating the observed luminosity functions, we find that LAEs' contribution to the cosmic star formation rate density rises with redshift until it is comparable to that from continuum-selected samples by z approximate to 6. This implies that LAEs may contribute more to the star-formation activity of the early Universe than previously thought, as any additional intergalactic medium (IGM) correction would act to further boost the Ly alpha luminosities. Linally, assuming fiducial values for the escape of Ly alpha and LyC radiation, and the dumpiness of the IGM, we integrated the maximum likelihood luminosity function at 5.00 < z < 6.64 and find we require only a small extrapolation beyond the data (<1 dex in luminosity) for LAEs alone to maintain an ionised IGM at z approximate to 6.
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| 9. |
- Evans, Aaron S., et al.
(författare)
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GOALS-JWST: Hidden Star Formation and Extended PAH Emission in the Luminous Infrared Galaxy VV 114
- 2022
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 940:1
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Tidskriftsartikel (refereegranskat)abstract
- James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) images of the luminous infrared (IR) galaxy VV 114 are presented. This redshift ∼0.020 merger has a western component (VV 114W) rich in optical star clusters and an eastern component (VV 114E) hosting a luminous mid-IR nucleus hidden at UV and optical wavelengths by dust lanes. With MIRI, the VV 114E nucleus resolves primarily into bright NE and SW cores separated by 630 pc. This nucleus comprises 45% of the 15 μm light of VV 114, with the NE and SW cores having IR luminosities, L IR(8 − 1000 μm) ∼ 8 ± 0.8 × 1010 L ⊙ and ∼ 5 ± 0.5 × 1010 L ⊙, respectively, and IR densities, ΣIR ≳ 2 ± 0.2 × 1013 L ⊙ kpc−2 and ≳ 7 ± 0.7 × 1012 L ⊙ kpc−2, respectively—in the range of ΣIR for the Orion star-forming core and the nuclei of Arp 220. The NE core, previously speculated to have an active galactic nucleus (AGN), has starburst-like mid-IR colors. In contrast, the VV 114E SW core has AGN-like colors. Approximately 40 star-forming knots with L IR ∼ 0.02-5 × 1010 L ⊙ are identified, 28% of which have no optical counterpart. Finally, diffuse emission accounts for 40%-60% of the mid-IR emission. Mostly notably, filamentary polycyclic aromatic hydrocarbon (PAH) emission stochastically excited by UV and optical photons accounts for half of the 7.7 μm light of VV 114. This study illustrates the ability of JWST to detect obscured compact activity and distributed PAH emission in the most extreme starburst galaxies in the local universe.
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| 10. |
- Hashimoto, T., et al.
(författare)
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The MUSE Hubble Ultra Deep Field Survey X. Ly alpha equivalent widths at 2.9 < z < 6.6
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 608
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Tidskriftsartikel (refereegranskat)abstract
- We present rest-frame Ly alpha equivalent widths (EW0) of 417 Ly alpha emitters (LAEs) detected with Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT) at 2.9 < z < 6.6 in the Hubble Ultra Deep Field. Based on the deep MUSE spectroscopy and ancillary Hubble Space Telescope (HST) photometry data, we carefully measured EW0 values taking into account extended Ly alpha emission and UV continuum slopes (beta). Our LAEs reach unprecedented depths, both in Ly alpha luminosities and UV absolute magnitudes, from log (L-Ly alpha/erg s(-1)) similar to 41.0 to 43.0 and from M-UV similar to -16 to -21 (0.01-1.0 L-z=3(*)). The EW0 values span the range of similar to 5 to 240 angstrom or larger, and their distribution can be well fitted by an exponential law N = N-0 exp(-EW0/w(0)). Owing to the high dynamic range in M-UV, we find that the scale factor, w(0), depends on M-UV in the sense that including fainter M-UV objects increases w(0), i.e., the Ando effect. The results indicate that selection functions affect the EW0 scale factor. Taking these effects into account, we find that our w(0) values are consistent with those in the literature within 1 sigma uncertainties at 2.9 < z < 6.6 at a given threshold of M-UV and LLy alpha. Interestingly, we find 12 objects with EW0> 200 angstrom above 1 sigma uncertainties. Two of these 12 LAEs show signatures of merger or AGN activity: the weak Civ lambda 1549 emission line. For the remaining 10 very large EW0 LAEs, we find that the EW0 values can be reproduced by young stellar ages (< 100 Myr) and low metallicities (less than or similar to 0.02 Z(circle dot)). Otherwise, at least part of the Ly alpha emission in these LAEs needs to arise from anisotropic radiative transfer effects, fluorescence by hidden AGN or quasi-stellar object activity, or gravitational cooling.
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